The Murphy 0-300 PSI Mechanical Lockout Pressure Swichgage 20P7-300 is a diaphragm-actuated, pressure-indicating gage with a built-in electrical switch. This swichgage is used for tripping alarms and/or shutdown devices. The gage mechanism is enclosed in a steel case coated to resist corrosion. A polycarbonate, break-resistant lens and a polished, stainless steel bezel help protect this rugged, built-to-last instrument. Accuracy and protection from moderate overpressure is assured by a unique, unitized diaphragm chamber. A built-in pulsation dampener helps eliminate pointer flutter and is removable for cleaning. This unit includes a front, semi-automatic lockout for startup override. This built-in device holds the pointer away from the contact on startup. When pressure exceeds the set point, the lockout is automatically disengaged.

The gage pointer acts as a pressure indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contacts are grounded through the Swichgage case and have self-cleaning motion to ensure electrical continuity. The gage pointer makes with an adjustable contact to complete a pilot-duty circuit.